Question on Problem 6A.19C in 7th Edition

[Sam Joslyn 1G]

This question asks to give the concentration of OH- in the solution that has a H₃O+ concentration of 3.1 mol*L^-1. Using the calculation [OH-]=K_w/[H30+], I got [OH-]=3.2*10^-15 mol*L^-1, but the book says 3.2*10^-12 mol*L^-1. Is there something I am missing?

[Emmaraf 1K]

I'm going to email my TA about this tomorrow but I think some questions in the 7th edition are incorrect in the cases where the pH/pOH aren't in the range of 0 to 14 since there are a few problems in the textbook (I remember one of them was a table where H+ and OH- concentration were 1.5M) where the concentrations of either OH- or H+ were above 1M meaning the complementary concentration would be less that 1x10^-14M and the pH and pOH would be greater than 14 or less than 0. From the information you provided, you seem correct and I ran into the same problem on a different question in the 7th edition so once I email my TA, I'll get back to this if nobody else responds.

[Sam Joslyn 1G]

I'm glad I am not the only person with this problem! Thank you.

[Emmaraf 1K]

I emailed my TA about some of the issues with negative pH in the 7th edition textbook and she agreed that it looked odd and would ask Dr. Lavelle about it. I think the solutions manual is just wrong in a few cases.